1. Field of the Invention
The present invention relates to a circuit breaker switching control system for turning on or turning off a circuit breaker at a desired phase of the power system voltage or main circuit current. In particular, it relates to technology for calculating the delay time of the power system voltage or main circuit current with respect to the zero-cross point, based on the circuit breaker switching actuation time and power system period, and for performing circuit breaker switching operation in accordance with this delay time.
2. Description of the Related Art
Techniques for controlling the opening or closing timing of a power circuit breaker in order to prevent generation of transient phenomenon in power systems or power equipment are already known. Such techniques for controlling the opening or closing timing of a circuit breaker are termed “synchronized switching control”. An example is ““Controlled switching of HVAC circuit circuit breakers. Guide for application lines, reactors, capacitors, transformers. SC13”, ELECTRA No. 183 P. 43 (1999)” (hereinbelow referred to as non-patent reference 1)”. In such a device that performs synchronized switching control, the closing or closing actuation time of the circuit breaker is detected and a synchronization delay time in respect of the opening or closure command signal of the circuit breaker is calculated, and the output timing of the opening or closure command signal is controlled in accordance with this calculated delay time.
However, the opening actuation time and closing actuation time of the circuit breaker vary depending on environmental conditions such as the ambient temperature or control voltage of the circuit breaker. The necessity of a function for estimating variation of the opening actuation time and closing actuation time in a device that performs synchronized switching control of a circuit breaker is discussed in non-patent reference 1.
For example, in the prior art disclosed in Laid-open Japanese Patent Application No. Tokkai 2001-57135 (hereinbelow referred to as patent reference 1), the variation of the opening actuation time or closing actuation time of the circuit breaker with respect to the control voltage is found at various different ambient temperatures, and The temperature characteristic and control voltage characteristic of the circuit breaker actuation time are thereby determined. The variation of the opening actuation time and closing actuation time of the circuit breaker that is the subject of such estimation on actuation is then estimated, using this temperature characteristic and control voltage characteristic, the control voltage of the circuit breaker that is the subject of such estimation, and the detected value of the ambient temperature. Also, in the prior art disclosed in patent reference 1, the variation of the opening actuation time or closing actuation time of the circuit breaker (this is called the actuation interval characteristic of the circuit breaker) is estimated, using the actuation interval of the circuit breaker.
Also, in the prior art disclosed in Laid-open Japanese Patent Application No. Tokkai 2001-135205 (hereinbelow referred to as patent reference 2), an opening actuation time correction table and closing actuation time correction table are created, based on environmental conditions that are measured beforehand, such as for example the circuit breaker control voltage and ambient temperature. The items recorded in these correction tables are one instance of the circuit breaker actuation time temperature characteristic and control voltage characteristic. The opening actuation time and closing actuation time are then estimated by correcting the standard opening actuation time and standard closing actuation time under the standard environmental conditions, using the opening actuation time correction table and closing actuation time correction table. If the circuit breaker operating mechanism is based on a hydraulic drive system, the opening actuation time and closing actuation time of the circuit breaker are affected by the hydraulic pressure. It is therefore also necessary to estimate the variation produced by the hydraulic pressure (this is called the circuit breaker hydraulic pressure characteristic).
However, in order to estimate the changes in the circuit breaker opening actuation time or closing actuation time based on the circuit breaker ambient temperature (hereinafter sometimes may be called the ambient temperature of the circuit breaker, others are the same), control voltage, operating hydraulic pressure and actuation interval etc, as in the prior art of patent reference 1 or patent reference 2, characteristic data such as the circuit breaker temperature characteristic, control voltage characteristic, hydraulic pressure characteristic and actuation interval characteristic, are necessary. Although, for these circuit breaker characteristic data, typically the same data can be employed if the model of circuit breaker used is the same, when the model of circuit breaker is different, the characteristic data are different for each model. Consequently, for each model of circuit breaker, various types of characteristic data must be measured beforehand in the model testing etc that is performed at the development stage, and these characteristic data must then be set beforehand as set values in the circuit breaker synchronized switching control device. By “the same model” is meant that the electrical characteristics and mechanical characteristics etc that are required in synchronized switching control are the same, excluding individual manufacturing variations.
Also, as stated in patent reference 1 etc, control taking into account the pre-arcing characteristic of the circuit breaker in synchronized closing control is indispensable. The pre-arcing characteristic must be calculated using the rate of decay of dielectric strength (RDDS), which is different for each model of circuit breaker. Consequently, the rate of decay of dielectric strength (RDDS) must be measured beforehand in the model testing etc that is performed on circuit breaker development, and this rate of decay of dielectric strength (RDDS) set beforehand in the circuit breaker synchronized switching control device.
If the manufacturer of the circuit breaker main unit and the manufacturer of the circuit breaker synchronized switching control device are the same, it is easy to set the necessary data such as the temperature characteristic, control voltage characteristic, hydraulic characteristic, actuation interval characteristic and rate of decay of dielectric strength (RDDS) etc of the circuit breaker in question in the synchronized switching control device of the circuit breaker prior to shipping. However, these data are typically difficult to acquire by a third party other than the manufacturer of the circuit breaker main unit. Consequently, when the manufacturer of the circuit breaker main unit and the manufacturer of the circuit breaker synchronized switching control device are different, it is difficult to set these data beforehand in the synchronized switching control device of the circuit breaker prior to shipping.
Furthermore, even when the manufacturer of the circuit breaker main unit and the manufacturer of the circuit breaker synchronized switching control device are the same, when for example a synchronized switching control device is added to an already-installed old circuit breaker, data such as the temperature characteristic, control voltage characteristic, hydraulic pressure characteristic, actuation interval characteristic and rate of decay of dielectric strength (RDDS) are not necessarily all available. Even if all the data are available, the precision of the data may be insufficient. In such cases, the models of circuit breaker with which a synchronized switching control device may be employed are restricted. Consequently, it is found that the application of a synchronized switching control device to an already-installed circuit breaker is difficult, or that the synchronized switching control device must be replaced when the circuit breaker is replaced.
Also, considered from the point of view of a user such as a power company, there is a possibility of economic disadvantage associated with the fact that, in power systems in which synchronized switching control is necessary, the purchasing source for the circuit breaker main unit or circuit breaker synchronized switching control device, or both of these, is restricted beforehand.
Even for circuit breakers of the same model, there are individual differences between circuit breakers in regard to the opening actuation time and closing actuation time under the standard conditions (typically corresponding to the opening actuation time and closing actuation time under the rated conditions) due to factors such as manufacturing variation. Consequently, the opening actuation time and closing actuation time must be measured for each circuit breaker in for example a shipping test and these data must be set in the synchronized switching control device of the circuit breaker prior to commencement of operation of the substation.
However, the opening actuation time and closing actuation time of the circuit breaker may change over a period of years, due to the effect of the number of times of circuit breaker actuation. Also, the rate of decay of dielectric strength (RDDS) may change over a period of years due to the effect of for example the number of times of interruption of the fault current or the magnitude of the fault current that is interrupted. It is therefore necessary to revise the set values of the synchronized switching control device in regard to data such as the opening actuation time and closing actuation time and rate of decay of dielectric strength (RDDS) in response to change over a period of years of the circuit breaker main unit. However, such revision of the set values was difficult to perform in the case of a conventional synchronized switching control device.